Mold growth in food materials, and particularly in animal feeds, is a problem when such materials are stored, such as in the case of hay, grain, and other forage materials. Molds are a type of fungi and are almost ubiquitous in small quantities due to the large number of their small spores in the environment. Common molds can include Acremonium, Alternaria, Aspergillus, Cladosporium, Fusarium, Mucor, Penicillium, Rhizopus, Stachybotrys and Trichoderma. Molds consume organic matter wherein humidity and temperatures are sufficient.
One reason molds present a problem is that some can produce dangerous mycotoxins. Mycotoxins are poisonous by-products produced by molds as they grow. Mycotoxins are known to be damaging to livestock when present in hay and other animal feed. For example, one of the common molds, Aspergillus flavus, produces the mycotoxin aflatoxin which, in addition to other toxic characteristics, interferes with the immune system's ability to produce gamma globulin, the protein that is part of the immune system. The resulting breakdown of the immune system then renders animals that have ingested such mold vulnerable to a variety of diseases.